What do you get if you try it from the context of a user mode program which has a gui component and has partially loaded enough to register some of its window classes / created its controls? Under these conditions win32k.sys should have kicked in by now I would think.

I believe this is due to the fact that win32k.sys' information is generally zeroe'd out in the PsLoadedModuleList. Only the driver name/path fields seem to contain any information. Russonivich's tool probably gets the DRIVER_OBJECT from the \Drivers\ folder in the object manager, which does contain correct information for Win32k.sys. I don't know why this is the case, but it seems to be on all Windows systems i've seen.